Expendable propellant casing



y 23, 1953 G. J. WALKEY ETAL 3,098,444

EXPENDABLE PROPELLANT CASING Filed Oct. 12, 1960 2 Sheets-Sheet 1 INVENTORS GEORGE J.WALKEY HOWARD B- SIPPLE VERNON S. SORENSON FRANK C. NORRIS Agent July 23, 1963 a. J. WALKEY ETAL 3,098,444

EXPENDABLE PROPELLANT CASING Filed Oct. 12, 1960 2 Sheets-Sheet 2 INVENTORS GEORGE-J-WALKEY HOWARD B. SIPPLE VERNON S. SORENSON FRANK C. NORRIS Agent 3,698,444 Patented July 23, 1963 iee 3,098,444 EXPENDABLE PROPELLANT CASING George J. Walkey, Burbank, Howard B. Sipple, Glendale,

Vernon S. Sorenson, La Crescenta, and Frank Norris, Sun Valley, Calitl, assignors to Lockheed Alrcraft Corporation, Burbank, Calif.

Filed Oct. 12, 1960, Ser. No. 71,855 1 Claim. (Cl. 102-43) The subject invention relates to the field of ordnance and ammunition in general and more particularly to an expendable propellant envelope or casing suitable for projectiles normally used in conjunction with a variety of weapons.

In the ordnance field, it has been conventional practice to employ ammunition having a metal envelope or casing for enclosing and holding a propellant charge and projectile forming a unitary construction which is placed into the breech of a weapon and ignited so that the projectile is propelled by the ignited propellant at high veloccity from the weapon. Inasmuch as the casing envelope is composed of metal, it is customary to provide suitable mechanisms within the breech of the weapon for ejecting the casing after ignition of the propellant and the firing of the projectile. Once the casing has been ejected, the casings are collected and returned to the ammunition manufacturer for reuse.

Difficulties have been encountered when employing the conventional ammunition casings which stem largely from the fact that the casings are composed of metal which is heavy and which requires ejection or removal from the breech of the weapon following the ignition of the explosive charge contained therein. Because of the weight of the casing, ordinary handling of the casing is difficult and the ejection and collection of used casings is a burdensome task.

The casing of the present invention obviates the above difficulties by providing a frangible and expendable propellant envelope or casing which will be combustible and frangible with the charge and which will leave no residue in the breech mechanism of the weapon firing chamber. The casing is composed of a plastic envelope material having a plurality of structurally weak areas so that the envelope materials are combustible or frangible by the ignited propellant. After the firing of the projectile, it is unnecessary to employ a method or mechanism for removing a used casing from the breech of the weapon.

In one form of the present invention, the plastic envelope or casing is made impervious to the elements and surrounding environment so that excellent protection is against such elements as salt spray, vapor transmission and environmental cycling. Such a construction is achieved by employing a Fiberglas cloth having a plurality of apertures therethrough which serves as an annular mandrel over which windings of plastic tape are provided to cover the Fiberglas cloth including the apertures so that a unitary construction is provided. The apertures provide areas of weakness in the construction. Upon ignition of the propellant within the casing, the casing will disintegrate without producing a flash or smoke. Because of the plurality of apertures provided in the casing, the plastic tape will burn out first and effect the continuous burning and weakening of the remaining Fiberglas cloth and tape within milliseconds after ignition so that complete disintegration of the envelope is achieved and any residue which might remain will be blown from the weapon breech.

Therefore, it is a primary object of the present invention to provide an expendable propellant casing which is capable of breaking into fragments of a size sufiiciently small that they will be blown out of the weapon chamber during firing of a projectile and/ or will not interfere with subsequent ammunition loading and firing of the weapon.

Another object of the present invention is to provide an expendable propellant casing having selective areas of weak costruction which is capable of withstanding normal handling and which will protect an enclosed propellant against adversed environmental conditions.

Still another object of the present invention is to provide a frangible and expendable propellant casing for enclosing propellant grains as well as a projectile which upon combustion will initiate a plurality of burning points about the casing which rapidly cause the complete disintegration of the casing within milliseconds from the initial ignition of the propellant grains.

Still another object of the present invention is to provide a thermoplastic casing for a propellant and projectile which can be made by high speed, continuous methods enabling the mass production of thermoplastic casing of either flexible or rigid forms at substantially lower costs than heretofore obtainable.

'Other objects of the present invention and the various advantages and characteristics of the present expendable casing will be apparent from a consideration of the following detailed description when taken in consideration with the accompanying drawings in which like numbers of reference denote corresponding parts throughout the several views; in which,

FIGURE 1 is a perspective view of a frangible casing in accordance with the present invention shown partially cut away to expose a perforated Fiberglas cloth mandrel;

FIGURE 2 is a cross-sectional view of the casing of FIGURE 1 taken in the direction of arrows 2-2;

FIGURE 3 is an enlarged frangible view of another embodiment of the invention shown in FIGURE 1 incorporating a cap fitted interiorly of the casing; and

FIGURE 4 is a side elevational view of the casing shown in FIGURE 1, partly broken away, employed to enclose and store a projectile and propellant grains.

Referring to the drawings, FIGURES 1 and 2 shows a casing 10 which comprises an inner layer 111 of glass fabric impregnated with a suitable polyester resin and the layer is suitably provided with a plurality of apertures, such as aperture 12, opening through both sides of the inner layer. The apertures may take the form of circular holes as shown in FIGURE 1; however, it is to be understood that other forms and configurations of apertures may be employed and that other arrangements of holes in either a predetermined or random fashion may be used.

It is preferred that inner layer 11 be of a continuous sheet which is cut to a prescribed length and width and then rolled so that a portion of the opposing edges of the sheet overlap to form a lapped joint 13 as shown in FIGURE 2. Since the Fibenglas cloth is impregnated with a plastic substance, the lapped joint may be readily achieved by applying pressure and heat to the joint followed by curing. In this fashion, the cylindrically formed Fiberglas inner layer 11 forms a perforated mandrel about which a second layer 14 of plastic material is disposed in order to close the apertures in the inner layer. The outer layer 14 is employed not only to cover the apertures provided in inner layer 11 but serves to give added rigidity and environmental protection for the entire assembly.

The outer layer 14 is shown in the embodiment of FIGURE 1 as a continuous tape which is spirally wrapped in place and distributed uniformly about the outer periphery of the inner Fiberiglas layer 11. The tape may be a suitable polyester resin impregnated glass fabric, for example. The joints between successive wrappings of tape may be slgihtly overlapped to insure that no gaps occur between adjacent turns of tape so that when spirally wrapped on the mandrel layer 11 the turns of tape are contiguous. However, since it is a primary object of the present invention to provide a structure or casing which is frangible and expendable, it is conceivable that the perforations may be left out of the inner layer and that the outer layer may provide points of weaknesses in the overall structure by spirally winding the tape to provide a slight gap between adjacent winds to provide areas of weaknesses in the structure.

The plastic material which impregnates the glass fabric maybe any natural or synthetic material of the type commonly known by the term plastic whether it be thermoplastic or thermosetting in character. The plastic material serves to bond the glass fabric together to render the casing wall impervious to the passage of fluids, and to contribute compressive strength sufficient to support the fibrous elements of the casing. While any plastic material can be used to perform these functions more or less well, it is generally advantageous to employ a composition of styrene and an alkyd resin as the plastic material, because the physical properties of this resin composition are particularly desirable for the most common used to which a casing of the present invention may be employed. Other synthetic resinous material that may be employed in making casing according to the invention are the vinyl halide resins and copolymers with vinyl esters, nylon, methacrylate resins, polyethylene, phenol-, ureaand melamine-formaldehyde condensation polymers, cellulose esters, and various blends of these and other materials. However, it is not essential that the plastic material employed be a synthetic resin. It may instead be a natural product such as a natural wax, resin or gum for those rather rare and infrequent uses where such materials have advantageous physical properties for the particular use to which the casing is to be put.

End 15 of the casing 11) is open to receive Whatever contents is to be placed within the casing or envelope while end 16 opposite to end 15 is provided with a cap 17 having an annular flange 18 which covers the external end surface of the outer layer. The cap is preferably molded of pre-impregnated glass mat for initiating the firing of the encased propellant.

With reference to FIGURE 3, cap 17 is shown as an alternate which fits into the interior of the hollow casing whereby the annular flange 18 snugly engages the inside diameter of the inner layer 11. To insure that cap 17 does not penetrate deeply into the interior of casing during its fitting, an inwardly annular rib or projection Wall 21 is employed extending inwardly from the inner wall which serves as a stop or abutment for the end of the annular wall 18 of the cap. Upon abutment of the wall 18 with wall 21, the cap will be properly placed. The cap may be secured to the casing by any suitable method.

With reference to FIGURE 4, the casing or envelope as shown in FIGURES 1 and 2 is illustrated in breakaway fashion showing a projectile 22 partially enclosed within the casing. Projectile 22, which is normally designated as a reeoilless projectile, includes an elongated body member 23 having a plurality of holes 24 commu nicating interiorly of the body for expelling hot combustion gases from the igniter cap 25 which is suitably arranged on the extreme end of body 23 and projected through aperture 20 of cap 17. Suitably attached to the body 23 of the projectile, there is provided a fin stabilizer means on the end thereof adjacent to end 16 of the casing for stabilizing the projectile during flight after firing from the casing and weapon. On the opposite end of body 23 from the stabilizing means 26, the projectile is provided with an explosive head 27 having an annular band or member 28 arranged in abutting engagement with the end 15 of the casing. It is to be noted that the projectile head 27 has a diameter which is the approximate diameter of the hollow of the casing so that the head may be pressfitted into the casing.

Between the projectile head 27 and casing end 16 is a storage area provided within the casing 10 into which propellant granules 30 or similar explosive propellant is stored. This area is represented in general by the numeral 31. The propellant granules surround the projectile body 23 and is in contact with apertures 24 provided therein through which hot combustion gases from the igniter cap 25 pass into contact with the propellant grains.

Upon ignition of the propellant grains, a spontaneous buildup of pressure within the hollow casing is produced which first forces a fracture or blowout through apertures 12 and adjacent walls of outer layer '14. This pressure blowout causes the entire casing to break into small fragments which immediately commence to burn and disintegrate. The pressure built up caused by the ignition of the propellant grains forces the projectile from the weapon into which the casing and projectile were placed. After the projectile has left the weapon and the weapons breech opened, there is substantially no residue or other material or fragments remaining in the breech which requires ejection or removal. The breech is substantially clean so that another round of ammunition may be placed within the weapons breech preparatory to firing.

Having described only typical forms of the invention we do not wish to be limited to the specific details herein set forth, but wish to reserve to ourselves any variations or modifications that may appear to those skilled in the art and fal-l within the scope of the following claim.

We claim:

A reeoilless tubular ammunition casing containing igni-table propellant, said casing comprising, an inner layer of oxidizable resin impregnated glass fabric, said inner layer having evenly distributed apertures therein, an outer layer of spirally wound oxidizable resin tape having glass fabric embedded therein bound to said inner layer and covering all of said apertures, said casing being frangible and disintegratable upon combustion of said propellant.

References Cited in the file of this patent UNITED STATES PATENTS 33,393 Johnston Oct. 1, 1861 2,703,529 Tuckerman et al. Mar. 8, 1955 2,837,456 Parilla June 3, 1958 12,956,500 Barr Oct. 18, 1960 2,971,426 Potts Feb. 14, 1961 

